Method Of Controlling A Wind Turbine In A Wind Power Plant

ABSTRACT

A method of controlling a wind turbine in a wind power plant, the wind turbine including a wind turbine controller and at least one connected wind turbine component, the wind turbine controller receiving data packets originating from a central controller, at least one of the data packets including instructions, the wind turbine controller performing the followings steps if one of the data packets includes a combined “write/read” instruction:
         effectuating a write instruction designated by the data packets,   retrieving information data resulting from the above effectuation of the write instruction from at least one of the wind turbine components,   transmitting the information data to the central controller upon reception of the information data from the at least one of the wind turbine components.       

     The invention performs a fast and simple control loop by means of transmitting both the write and the read instruction within one single data packet.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of pending Internationalpatent application PCT/DK2007/000260 filed on May 31, 2007 whichdesignates the United States, the content of which is incorporatedherein by reference.

FIELD OF THE INVENTION

The invention relates to a method of controlling a wind turbine in awind power plant, the wind turbine comprises a wind turbine controllerand at least one connected wind turbine component,

BACKGROUND OF THE INVENTION

The strategically distributed nature of wind power presents uniquechallenges. A wind power plant comprises several wind turbines and maybe located offshore, and it often covers large geographic areas.

These factors usually require a variety of networked interconnectionsand telecommunication technologies for monitoring and controlling windpower electric generating facilities which often are referred to asSCADA (SCADA: Supervisory Control And Data Acquisition).

The prior art presents several ways of controlling a wind turbine andwind power plants. U.S. Pat. No. 6,966,754 teaches a method formonitoring wind turbines, by means of image and acoustic monitoring.This is an example of a wind turbine to control itself on the basis ofdynamical measurement of factors within the wind turbine. Europeanpatent application EP 1519040 discloses a method for a remote readingand changing of power settings in wind turbine generators.

Today, the focus has moved from the separate turbine connection pointsto the central wind power plant connection point, often referred to asthe “point of common coupling” (PCC). One of the most limiting factorswhen performing central control of a wind power plant with several windturbines is the time it takes to gather information from all turbinesand distributing control data, e.g. new active or reactive power setpoints to all turbines. This may be a problem since the requirements towind power plant response times have increased considerably during therecent years. It is an object of the invention to provide a fastercommunication to and from wind turbines, thereby optimizing the centralcontrol of wind power plants.

SUMMARY OF THE INVENTION

The present invention relates to a method of controlling a wind turbine(WT) in a wind power plant (WPP),

the wind turbine comprises a wind turbine controller (WTC) and at leastone connected wind turbine component (WTCO), the wind turbine controller(WTC) receiving data packets (DP) originating from a central controller(CC), at least one of said data packets comprising instructions, the WTCperforming the followings steps if one of said data packets (DP)comprises a combined “write/read”” instruction (WRI):

-   -   effectuating a write instruction designated by said data packets        (DP),    -   retrieving information data (ID) from at least one of said wind        turbine components (WTCO),    -   transmitting said information data to said central        controller (CC) upon reception of the information data from at        least one wind turbine component (WTCO).

In an embodiment of the invention, said method is performed within onecontrol loop execution in said central controller (CC).

The term “wind power plant” is according to the present inventionunderstood as a facility with one or multiple wind turbines operating asa single power plant and interconnected to the utility grid at a singlepoint. Wind power plants are also called wind farms, wind powerstations, wind plants, wind parks, and wind energy projects. A windpower plant comprises a number of wind turbines located in the same areain a group onshore or offshore. The wind turbines may be assembled toconstitute a total unified power producing unit that can be connected tothe utility grid. A wind power plant typically has a “master” or centralcontroller. The central controller may according to an embodiment of theinvention be located as part of or in relation to a Supervisory ControlAnd Data Acquisition (SCADA) server. The central controller may berelated to a control station or substation which may comprise a numberof computers or processing units. The central controller may also have aprocessing unit and may typically comprise means for or processing unitscontinuously monitoring the condition of the wind turbines and collectstatistics on their operation and may at the same time send controlinstructions to the wind turbines. The central controller may alsocontrol a large number of switchgears, hydraulic pumps valves, andmotors within the wind turbine, typically via communication with thewind turbine controller of the wind turbine.

The term information data is in accordance with an embodiment of theinvention understood as any data comprising wind turbine information.This may e.g. be measure data from wind turbine components, or it may beinformation of the active or reactive power set point of the windturbine. If a central controller has transmitted a active or reactivepower set point to a given wind turbine controller, the information dataretrieved from a wind turbine component may be the present active orreactive power set point of the wind turbine. The wind turbine may as itis have another active or reactive power set point than the one sent inthe “write/read” instruction. This may be possible if for example notthere is enough wind to match the active or reactive power set point ofthe “write/read” instruction.

In an embodiment of the invention, only one single data packet istransmitted from the central controller (CC) to the wind turbinecontroller (WTC) during one control loop execution in the centralcontroller (CC).

The term “data packet” is according to an embodiment of the inventionunderstood as any type of data packet, frame or datagram comprisinginformation data. A data packet may comprise at least three elements:firstly a header, which marks the beginning of the packet and containsthe source and destination address; secondly the payload, which containsthe data to be carried inside the packet; and thirdly the trailer, whichmarks the end of the packet and contains a checksum to check if thepacket was corrupted during transmission. Examples of a data packet arean IP (internet protocol) packet, a TCP data packet or a UDP (UserDatagram Protocol) data packet. An IP packet is a chunk of datatransferred over the Internet using standard Internet protocol (IP).Each packet begins with a header containing addressing and systemcontrol information. TCP is a connection-oriented protocol, which meansthat a connection is established and maintained until such time as themessage or messages to be exchanged by the application programs at eachend have been exchanged. UDP is a transport layer protocol in the TCP/IPprotocol suite that allows an application program on one host to send aconnectionless datagram to an application program on another host.

The terms “write/read” packet, “write/read” telegram or “write/read”instruction is in accordance with the invention understood as a datapacket that comprises both an instruction to write and an instruction toread. There may be several practical implementations of the system thatsupports “write/read” packets. For example, a software component in awind turbine controller may recognize a “write/read” data packet andthereupon effectuate a write instruction and subsequently effectuate aread instruction of some of the wind turbine components. A data sequencecomprising a “write” instruction immediately followed by a “read”instruction is within the scope of the invention.

Wind turbine components are in accordance with the present inventionunderstood as equipment in the wind turbine. This may be sensors, metersor actuators.

In an embodiment of the invention, said data packet (DP) is an IPpackage.

In accordance with the invention, the term “control loop” is understoodas a continuously repeated process, which for eachexecution/repetition/loop typically executes at least the followingthree steps:

-   -   obtaining information data related to the wind power plant from        the wind turbine in the central controller,    -   performing a comparison of the information data with predefined        data to determine an error, and    -   performing a regulating action by means of transmitting a        “write” instruction to the wind turbine according to the error.

The present invention performs a fast and simple control loop by meansof transmitting both the write and the read instruction to the windturbine controller within one single data packet. Conventionally, readinstructions and write instructions were sent in two or more differentdata packets. Thus, the present invention may reduce the time of asingle evaluation of the control loop by half, which is a very effectiveoptimization of the response time of the wind power plant.

Moreover, the invention relates to a method of controlling a windturbine from a central controller in a system of at least two windturbines, wherein said central controller performs the step oftransmitting at least one “write/read” telegram to the wind turbinecontroller.

In an embodiment of the invention, said “write/read” instruction istransmitted to said wind turbine controller within one control loopexecution.

In accordance with the invention, the term control loop is understood asa continuously repeated process, which for each repetition/looptypically executes at least the following three steps:

Obtaining one or several measurements from sensors in the wind powerplant,

performing a comparison of the measurements with a predefined “active orreactive power set point” to detect an error, and performing aregulating action by means of transmitting a “write” instruction to thewind turbine according to the error.

Thus, a control loop in accordance with the invention is understood as a“feedback loop”

In an embodiment of the invention, said “write/read” telegram comprisesboth an instruction to write values and an instruction to read values inthe wind turbine.

In an embodiment of the invention, said “write/read” telegram comprisesan instruction to write values, an instruction to read values, andwherein said wind turbine controller responds to the “write/read”instruction by means of transmitting a response telegram comprising arepresentation of the read values, to the wind turbine.

In an embodiment of the invention, said response telegram comprises arepresentation of at least one value read in the wind turbine.

In an embodiment of the invention, said “write/read” telegram isallocated higher transmission priority by the wind turbine controller(WTC) and intersection points of the data communication network (DCN).

Intersection points are in accordance with the present inventionunderstood as any point where the data communication network intersects.Examples are switches, links routers, etc.

Moreover, the invention relates to a wind turbine controller comprisedin a wind turbine and being connected to at least one wind turbinecomponent (WTCO), wherein the wind turbine controller (WTC) is arrangedfor receiving data packets (DP) originating from a central controller(CC), where at least one of said data packets comprising instructions,wherein the wind turbine controller (WTC) is arranged for performing thefollowing steps if one of said data packets (DP) comprises a“write/read” instruction (WRI):

-   -   effectuating a write instruction designated by the “write/read”        instruction (WRI)    -   retrieving information data (ID) from at least one of said wind        turbine components (WTCO),    -   transmitting information data (ID) to said central        controller (CC) upon reception of the information data (ID) from        at least one wind turbine components (WTCO).

Hereby, the invention relates to a wind turbine controller, adapted forresponding to a “write/read” telegram by means of writing/setting atleast one value in the wind turbine, reading at least one value in thewind turbine and transmitting a representation of said value back to thecentral controller station (CC).

Furthermore, the invention relates to a wind power plant systemcomprising at least two wind turbines, at least two wind turbinecontrollers according to the invention and related to said windturbines, a central controller connected to said wind turbines via saidwind turbine controllers via a data communication network, wherein thecommunication between said central controller and said wind turbinecontrollers is performed by utilizing a communication protocolsupporting “write/read” telegrams.

In an embodiment of the invention, said “write/read” data packetscomprises information of active power.

Moreover, the invention relates to use of read/write instructions in anetwork of wind turbines.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following with reference to thefigures in which

FIG. 1 illustrates a large modern wind turbine as seen from the front,

FIG. 2 illustrates an overview of a typical wind power plant,

FIG. 3 illustrates a simplified example of the communication between thecentral controller and the wind turbine,

FIG. 4 illustrates the data network of a wind power plant according toan embodiment of the invention, and

FIG. 5 illustrates a flowchart of the steps in a wind turbine controlleraccording to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a modern wind turbine 1. The wind turbine 1 comprisesa tower 2 positioned on a foundation. A wind turbine nacelle 3 with ayaw mechanism is placed on top of the tower 2.

A low speed shaft extends out of the nacelle front and is connected witha wind turbine rotor through a wind turbine hub 4. The wind turbinerotor comprises at least one rotor blade e.g. three rotor blades 5 asillustrated.

FIG. 2 illustrates an overview of a typical wind power plant WPPaccording an embodiment of the invention. A wind power plant may in somecontexts be referred to as wind parks or wind farms. A wind power plantcomprises a number of wind turbines WT located in the same area in agroup onshore or offshore. The wind turbines may be assembled toconstitute a total unified power producing unit that can be connected tothe utility grid. A wind power plant typically has a “master” or centralcontroller CC. The central controller CC may according to an embodimentof the invention be located as part of or in relation to a SCADA server.The central controller CC may be related to a control station orsubstation which may comprise a number of computers or processing units.The central controller CC may also have a processing unit and maytypically comprise means for continuously monitoring the condition ofthe wind turbines and collect statistics on its operation and may at thesame time send control instructions to the wind turbines. The centralcontroller CC may also control a large number of switchgears, hydraulicpumps valves, and motors within the wind turbine, typically viacommunication with the wind turbine controller WTC of the wind turbine.The central controller CC may be connected to the wind power plantnetwork DCN locally or remotely via a data communication network DCN ora public data communication network PDCN, e.g. the internet. Controlrelated data may be transmitted to and from the wind turbines WT via adata communication network DCN. The wind turbines may via the datacommunication network be serial or parallel connected or any combinationthereof. The control data may typically be data to control a windturbine. This may e.g. be instructions to a given wind turbine to changethe set point of produced power. Simultaneously, the data communicationnetwork DCN is utilized for transmitting monitoring data from the windturbines in the wind power plant WPP to the central controller CC. Thismay e.g. be a reading of a pressure meter of a valve of the windturbine. The data communication network DCN may e.g. comprise a localarea network LAN and/or a public data connection network, e.g. theinternet.

FIG. 3 illustrates a simplified example of the communication between thecentral controller CC and the wind turbine WT according to an embodimentof the invention. The figure illustrates a wind turbine WT comprising awind turbine controller WTC and wind turbine components WTCO. Moreover,the figure illustrates the central controller CC and the wind turbinecontroller being connected via a data communication network which may bedirected via a public data communication network, e.g. the internet. Thearrows on the figure illustrate data packets comprising a “write/read”instruction WRI, data packets comprising information data ID, and a datapacket comprising a write instruction WI.

A “write/read” instruction WRI comprised in one single data packet maybe transmitted from a central controller CC to the wind turbinecontroller WTC via a data communication network or a public datacommunication network as a part of a control loop. The wind turbinecontroller WTC may upon receipt of the “write/read” data packeteffectuate the write instruction in one or several wind turbinecomponents WTCO. Subsequently, the wind turbine controller WTC may inaccordance with an embodiment of the invention receive information dataID from one or several wind turbine components WTCO. The wind turbinecontroller WTC may thereupon transmit the information data to thecentral controller CC. This information data ID, may then be utilized inthe control loop to calculate the next active or reactive power setpoint to be transmitted in the next “write/read” instruction. Thus, onlyone single data packet is transmitted from the central controller CC tothe wind turbine controller WTC and one data packet is transmitted backto the central controller CC during one single control loop of thecentral controller CC.

FIG. 4 illustrates the data network of a wind power plant WPP accordingto an embodiment of the invention. The figure illustrates a number ofwind turbines WT, a central controller CC, and a number of switches SW.Each of the wind turbines WT comprises or is related to a wind turbinecontroller WTC. Furthermore, the figure illustrates a data communicationnetwork DCN. The central controller CC may comprise or be related to aSCADA server. Wind turbine controllers may be located inside the relatedwind turbines WT, e.g. in the tower, the nacelle, etc., or it may belocated outside the wind turbines WT.

In order to control the wind turbines of the wind power plant WPP, thecentral controller CC performs a control loop, which e.g. may comprisethe following steps.

-   -   obtaining information data from the wind power plant WPP,    -   performing a comparison of the information data with predefined        data to determine an error, and    -   performing a regulating action by means of transmitting a        “write” instruction to the wind turbine according to the error.

The present invention performs a fast and simple control loop by meansof transmitting both the write and the read instruction to the windturbine controller within one single data packet. Conventionally, theread and the write were sent in two different data packets. Thus, thepresent invention may reduce the time of a control loop by half, whichis a very effective optimization of the response time of the wind powerplant WPP.

In this figure it is illustrated that data packets DP, e.g. a“write/read” packet transmitted between a central controller CC and thewind turbines WT typically must pass several intersection points, i.e.switches SW, to reach its destination. Thus, it is of great importancethat the number of data packets is minimized to optimize the expenditureof time.

It should be noted that the illustrated daisy chaining of networkcomponents WTCO merely represents one of several applicable networkstructures.

It should furthermore be noted that the present figure is only one ofseveral applicable data communication networks of a wind power plant WPPin which the present invention may be implemented.

Examples of data to be read in relation with a wind turbine, in relationto the wind turbine controller WTC to be transmitted back to the centralcontroller upon receipt of a “write/read” instruction are:

-   -   “Active power measurement”. Active power is the total power        generated by the wind turbine to be directly used.    -   “Power Set Point” refers to the desired power to be produced by        a given wind turbine WT.    -   “available power” refers to the possible available energy in the        present wind conditions.    -   “Turbine run state” comprises information of the current run        state of a wind turbine e.g. if the wind turbine is shut off.    -   “Reactive power measurement”. The flow of electrical energy from        an inductive or capacitive load across a circuit towards a        generator. Measured in volt-amperes-reactive (VAR), the        conventional symbol for reactive power is “Q”. Reactive power        results when current is not in phase with voltage—and can be        corrected using e.g. capacitors, statcom or other devices.

Examples of a write instruction data to be sent from a centralcontroller CC as a part of a “write/read” packets, are listed in thefollowing:

-   -   “Active power set point”. An instruction of setting reactive        power to a given value.    -   “Reactive power set point”. An instruction of setting active        power to a given value.    -   “Power Factor set point”. An instruction of setting Power Factor        (Cos(phi)) to a given value.    -   “Turbine run state” An instruction of setting turbine run state        to a given state, e.g. “off”.

It should be noted that many other data than the above-mentionedexamples may in accordance to the present invention be allocated highertransmission priority.

FIG. 5 illustrates a flowchart of the steps in a wind turbine controllerWTC according to an embodiment of the invention. In step 1, the windturbine controller WTC receives a data packet. This may be in a dataport of the wind turbine controller WTC or at a protocol handler. Instep 2. it is determined whether the received data packet DP is a“write/read” data packet. If no, the wind turbine controller reads thedata packet and acts upon it if relevant. If the data packet DP is of a“write/read” type, the wind turbine controller WTC effectuates the writeinstruction in step 4. This will typically involve a write instructionto wind turbine components WTCO, e.g. an instruction to change the powerset point. Subsequently, the wind turbine controller retrievesinformation data from the wind turbine components WTCO in step 5. Thismay take some time. When all desired data is read from the wind turbinecomponents WTCO, or a predefined time limit has expired, the windturbine controller WTC transmits the information data to the centralcontroller CC in step 6.

1. A method of controlling a wind turbine in a wind power plant, thewind turbine comprising a wind turbine controller and at least oneconnected wind turbine component, the wind turbine controller receivingdata packets originating from a central controller, at least one of saiddata packets comprising instructions, the wind turbine controllerperforming the followings steps if one of said data packets comprises a“write/read” instruction: effectuating a write instruction designated bythe “write/read” instruction, retrieving information data from at leastone of said wind turbine components, and transmitting said informationdata to said central controller upon reception of the information datafrom the at least one of said wind turbine components.
 2. The method ofcontrolling a wind turbine according to claim 1, wherein said method isperformed within one control loop execution in said central controller.3. The method of controlling a wind turbine according to claim 1,wherein only one single data packet is transmitted from the centralcontroller to the wind turbine controller during one control loopexecution in the central controller.
 4. The method of controlling a windturbine according claim 1, wherein said data packet is an internetprotocol packet.
 5. A method of controlling a wind turbine from acentral controller in a system of at least two wind turbines, whereinsaid central controller performs the step of transmitting at least one“write/read” telegram to a wind turbine controller.
 6. The method ofcontrolling a wind turbine according to claim 5, wherein said“write/read” telegram is transmitted to said wind turbine controllerwithin one control loop execution.
 7. The method of controlling a windturbine according to the claim 6, wherein said “write/read” telegramcomprises both an instruction to write values and an instruction to readvalues in the wind turbine.
 8. The method of controlling a wind turbineaccording to claim 5, wherein said “write/read” telegram comprises aninstruction to write values, an instruction to read values, and whereinsaid wind turbine controller responds to the “write/read” instruction bymeans of transmitting a response telegram comprising a representation ofthe read values, to the wind turbine.
 9. The method of controlling awind turbine according to claim 8, wherein said response telegramcomprises a representation of at least one value read in the windturbine.
 10. The method of controlling a wind turbine according to claim5, wherein said “write/read” telegram is allocated higher transmissionpriority by the wind turbine controller and intersection points of thedata communication network.
 11. A wind turbine controller comprised in awind turbine and being connected to at least one wind turbine component,wherein the wind turbine controller is arranged for receiving datapackets originating from a central controller, where at least one ofsaid data packets comprising instructions, wherein the wind turbinecontroller is arranged for performing the following steps if one of saiddata packets comprises a “write/read” instruction: effectuating a writeinstruction designated by the “write/read” instruction retrievinginformation data from at least one of said wind turbine components, andtransmitting information data to said central controller upon receptionof the information data from the at least one of said wind turbinecomponents.
 12. A wind power plant system comprising at least two windturbines, at least two wind turbine controllers according to claim 11and related to said wind turbines, a central controller connected tosaid wind turbines via said wind turbine controllers via a datacommunication network, wherein communication between said centralcontroller and said wind turbine controllers is performed by utilizing acommunication protocol supporting “write/read” telegrams.
 13. A systemof at least two wind turbines according to claim 12, wherein said“write/read” data packets comprises information of active power.
 14. Useof “write/read” instructions in a network of wind turbines.